The present invention relates to control of electronic devices and systems, and more specifically to methods and systems for digital control of electronic power devices and other systems that require similar control functions. Applications of power electronics include power supplies, lighting, UPS, motion control and more.
In computer power supplies, the applications include low voltage-high current and fast controlled power supplies for advanced central processing units (CPUs) and other integrated circuits (ICs) of the same technology. The state of the art topology for this application is represented by the multi-phase synchronous rectifier buck, e.g. the XPhase™ Scalable Multi-Phase Architecture using IR3081 & IR3086 ICs from International Rectifier Corp., 233 Kansas St. El Segundo, Calif. 90245.
In lighting, the applications include state of the art electronic ballasts for fluorescent lamps use, analog ICs for their power stages (PFC stage and half-bridge stage), and use of small microprocessors for digital communication of commands of the lamp. Typical implementations may use by example an IC controller such as L6561D from SGS Thomson, 1060E. Brokaw Road, San Jose, Calif. 95131 for the PFC stage, and an IC controller such as IR2159 from International Rectifier Corp. for the half-bridge stage. The PIC 16C628 microcontroller from Microchip Corp., 2355 West Chandler Blvd., Chandler, Ariz. 85224-6199, may be used for ballast management and communication.
For UPS, applications include microprocessors for ballast management and communication, (see feature article “On Line UPS”-“DSP provide High-Speed, Cost Effective Solution” PCIM magazine, August 1999) using a digital signal processor (DSP), e.g. device TMS320C24 from Texas Instruments (TI), 12500 TI Boulevard Dallas, Tex. 75243-4136 or a more advance device like TMS320F2810.
In motion control, where the main demands include high precision, complex mathematical algorithms and usually moderate speed, the state of the art controls for motors use by example a DSP such as TMS320C24 from TI. This is a fixed DSP device with embedded read only memory (ROM), instead of code-configurable with flash memory, as in devices like TMS320F240. The configurability of this DSP is limited to the specific mode of operation of its Pulse Width Modulators (PWM) outputs. An example of this is the PWM output configuration by means of a register that inserts an appropriate dead band between two PWMs, and another register that fixes the polarity of the PWM channels (Application Report SPRA289 from TI). In this case, there is no configurable event-driven pulse sequence generation by means of a look-up table (LUT). The recently launched TI TMS320F28x family is intended for multi-axis/motion-control applications. The devices comprise a module called Event Manager that allows a limited configuration of the PWM outputs. The calculations and the analog and digital measurements processing in the present invention is done independently by the custom logic. This is contrary to the approach used in TI devices in which the CPU performs these tasks. In addition, programming (definition) of the configurability in the present invention is performed without code programming, whereas in the TI devices it is done by programming of the CPU software.
The state of the art includes also some digital reconfigurable solutions, generally using field-programmable gate arrays (FPGA), together with some analog front-end analog-to-digital converters (ADC) for the analog inputs of the control mechanism. A generic programmable logic device like a FPGA device or a CPLDs, by example EP20K400FC672-1 from Altera Corp., 101 Innovation Drive San Jose, Calif. 95134, targets the general case and sacrifices performance and area in order to achieve a high degree of flexibility. This extreme level of flexibility is unnecessary and would result in significant silicon area (high cost), delay (latency), and high power consumption.
The need for custom fabrication provides the opportunity to tailor a reconfigurable hardware to the intended uses and applications of a system on chip (SoC), instead of the high cost of development and the long time-to-market characterized by the application of a proprietary ASIC solution.
To summarize, at present, both analog and digital control solutions suffer from a number of disadvantages. Analog control solutions show degradation due to component aging and component temperature drift. They require more parts (lower reliability), have limited upgrades, and present difficulty of integrator clamping and preset. Digital control solutions exhibit latency, have limited bandwidth (fBW=fS/10 to fS/6) (the maximal bandwidth of such solution cannot be more than the switching frequency divided by 6) and the design is more difficult and needs the programming of the DSP CPU core.
In view of the prior art disadvantages mentioned above, there is a widely recognized need for, and it would be highly advantageous to have an apparatus and method, that provide fully configurable digital control for various power applications, instead of proprietary ASIC solutions with their attendant disadvantages in terms of high cost and long time-to-market.